Coupling device for concentric conductor lines



oct. i2, 1948. A, ROBlNsoN 2,451,413

GOUPLING DEVICE FOR CONCENTRIC CONDUCTOR LINES Filed Dec. 20,. 1945 /N l/E /V TOR A. L. RUB/NSN A TTOFP/'VEV Patented Get. 12, 1948 COUPLING DEVICE FOR CONCENTRIC CONDUCTOR LINES Albert L. Robinson, South Orange, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of Neu7 York Application December 20, i943, Serial No. 514,947

7 Claims. (Cl. 178-44) This invention relates to a concentric conductor transmission line for high frequency signal waves, and more particularly to a coupling device for connecting adjacent sections of the inner and outer conductors such that reflection effects are substantially minimized.

The present invention is especially concerned with connecting concentric conductor sections in which the individual inner conductors tend to vary in length with reference to the lengths of their associated outer conductors.

The present invention contemplates a device for coupling the ends of adjacent sections of outer and inner conductors of a concentric transmission line such that the coupling is capable of expeditious assembly and disassembly together with inspection for tightening-up purposes and such that the coupling tends compensate for variations in the relative lengths of associated sections of outer and inner conductors, thereby permitting interchangeability of the inner conductor sections.

The main object of the invention is to provide a coupling for expeditiously assembling and disassembling individual sections of a concentric conductor transmission line.

Another object is to provide a coupling of variable eifective length.

A further object is to provide a coupling which tends to minimize reiiection effects during the transmission of high frequency waves.

Another object is to provide a concentric conductor transmission line in which the inner conductors of individual line sections are interchangeable.

A familiar concentric conductor line for transmitting intelligence by means of high frequency waves comprises a plurality of sections of outer and inner conductors, and suitable insulators for maintaining a concentric relation between the inner and outer conductors. In assembling these conductors into an operative line extend-ing between a source of signal waves and a load therefor, it has been found that the lengths of the individual sections of outer and inner conductors tend to vary, with reference to each other, from line section to line section. Accordingly, a coupling for joining such line sections should, among other requirements, be capable of compensating for variations in the lengths of the inner conductors with reference to their associated outer conductors.

A specific embodiment of the present invention comprises means for connecting the ends of adjacent sections of outer conductor, comprising a pair of sleeves one of which is disposed on the end of each section, a bipart spacing member interposed between the sleeves, and an external collar for holding the sleeves and spacing member in the assembled relation; and means for connecting the ends of adjacent sections of inner conductor, comprising a plug having one end positioned in one end of each of the adjacent sections of inner conductor, and the opposite end formed with a peripheral projection bearing against the end of the associated inner conductor, a iiange, and a shank joining the projection and ange, and a clamp comprising a pair of semi-circular members assembled to provide eiectively a pair of oppositely disposed recesses each of which accommodates one flange such that individual flanges are displa-ceable to various positions in the associated recesses to compensate for the variations in the lengths of the inner conductor sections, with reference to their associ-- ated outer conductor sections.

A feature of the invention is that the couplings can be inspected from time to time for tightening-up purpose, particularly when employed in mobile apparatus, such as trucks, ships, and tanks,

which tend to subject their loads to intense shocks from time to time. Moreover, since the outer conductors may be fixed in position, the coupling serves to compensate for reasonable variations in the lengths of the inner conductor sections with reference to their associated outer conductor sections. In addition, the coupling tends to sectionalize the entire line such that individual line sections may be disassembled and reassembled without disturbing the remainder of the line; and to permit interchangeability of sections of inner conductor.

The invention will be readily understood by reference to the following description taken together with the accompanying drawing, in which:

Fig. 1 illustrates an assembled concentric conductor line which embodies the present invention;

Fig. 2 shows the specic embodiment of the present invention;

Fig. 3 is a cross-sectional view taken along the line 3-3 in Fig. 2;

Fig. 4 is an elevational View showing a plug used in the invention;

Figs, 5 and 6 are left-hand and right-hand end views, respectively, of Fig. 4;

Fig. 7 is an elevational view of a bipart clamp used in the invention;

Fig, il is an end view of Fig. 7; and

Fig. 9 is a cross-sectional view taken along the line S-S of Fig. 2.

Referring to Figi, a concentric conductor line I comprises a plurality of sections or" outer conductor Il and a plurality of sections of inner conductor I2. These conductors are concentrically spaced by suitable insulators I3 such, for example, as in the manner illustrated in the patent to P. H. Smith, No. 2,280,200, granted April 21, 1942. This tends to maintain a certain ratio between the inside diameter of the outer conductor and the outside diameter of the inner conductor so as to provide the individual line sections substantially with the same characteristic impedance as disclosed in the patent of E. I. Green, No. 1,841,473, granted January 19, 1932. The left-hand end of the transmission line is applied to a transmitter i4 while the right-hand end is connected to an antenna I5. This line serves to transmit high frequency waves employed in intelligence signal systems in the familiar manner.

In accordance with the present invention, the ends oi adjacent sections of outer and inner conductors are joined together by a plurality of couplings i6 which will now be described. Referring to Fig. 2, the end of the left-hand section 'of outer conductor H is provided with a sleeve 26 formed with a central threaded portion 2l and a shoulder 22 bearing against the end of the outer conductor. The right-hand section of outer conductor Ii is provided with a sleeve 23 formed with an outer end threaded portion 21%, an intermediate peripheral projection 25, and a shoulder 26 bearing against the end of the outer conductor. A -bipart spacing member 21 split radially at 28, Figs. 3 and 9, is positioned between the outer surfaces of both shoulders 22 and 26. An external coupling 3B joins together the sleeves 2@ and 2?, and the spacing member 2l. A nut 3l locks the coupling 3s in position.

In the hollow end of the left-hand section of inner conductor l2 is disposed one end oi a circular plug 3l formed on its opposite end, as shown in Fig. 4, 'with a peripheral projection 32, a iiange 33, and a shank 3d interposed therebetween. The inner face of the peripheral projection 32 bears against the end of the associated inner conductor. Another plug 3l is also positioned in like manner in the hollow end of the right-hand section of inner conductor. A clamp t serves to connect -the oppositely disposed plugs. Referring to Figs. 'I and 8, the clamp @il comprises an upper semicircular member il and a lower semicircular member ft2. The upper member includes a recess 43 and an opening 44 both of which accommodate the upper end of a screw 46 whose lower end is received in a suitably threaded opening d'1. This screw serves `to maintain the members fil and i2 in the assembled relation in electrical contact with the plugs 3 l, 3l in a manner that will be subsequently pointed out. In each of the opposite ends of the clamp is eiectively formed an annular recess 68 whose one wall 45 comprises portions oi both members lil and l2 and whose other walls -59 and 5I comprise extensions of both latter members. The outer wall l is formed by a semiannular projection 52 on each of the members il and @2. Referring to Fig. 2, the clamp til is assembled on the plugs 3l, 3i lsuch that electrical contact is established therewith by means of the Shanks 34, 3i and the semiannular projections '52, 52, and the inner surfaces 5G, 5E and the flanges 33, 33.

Accordingly, electrical contact may be established at diiierent spaced points on the plugs 3i, 3| depending on the lengths of the sections of inner conductor being joined together, with reference to the lengths of the associated sections of outer conductor. Such different points of electrical contact are established by unscrewing the screw 46 and moving both plugs relative to the clamp, which is in one lassumed case maintained substantially stationary, such that individual anges are di-splaceable to dilerent positions in their associated recesses; or ixing the plugs in position and moving the clamp relative thereto which is another assumed case; or fixing one plug in position and moving both the clamp and the other plug relative thereto which is a further assumed case. Thus, the assembled plugs and clamp are of variable eiective length; Iand the plugs and clamp may be individually moved to change their relative positions and thereby to vary the effective length of such assembly. Hence, this 4characteristic of variable effective length is advantageous for connecting adjacent line sections in each of which the lengths of the individual sections of inner conductor tend to vary with reference to their associated sections of outer conductors forthe reason that such characteristic tends to compensate for the variations in the relative lengths of the associated inner and outer conductors of individual line sections.

In the assembly of the transmission line together with the plugs and clamp as illustrated in Fig. 2, it will be noted that the ratio between the inside diameter of the outer conductor and the outside diameter of the inner conductor is substantially uniform except at several spaced points along the longitudinal axis of the assembly of the plugs land clamp, at each of which points variations in this ratio occur. The effect of such ratio variations is to provide an impedance mismatch at these points, with yelference to the characteristic impedance of the individual line sections as disclosed in the Green patent, supra. As a consequence, the point-s of such ratio vari-ations tend to introduce reflection effects during the transmission of the high frequency currents and thereby tend to introduce loss in the intelligence being transmitted. Such reiiection eiects and impedance mismatch may be compensated for by making the electrical length of the clamp a quarter wavelength, or an odd multiple of one-quarter Wavelength at the mean frequency of the waves being transmitted on the concentric conductor line. In other words, such coupling assembly provides an electrical path of low loss for the waves being transmitted on the concentric conductor line extending between the transmitter and receiVer, Fig. 1; while at the same time enabling expeditious accomplishment of the features hereinbefore mentioned.

What is claimed is:

1. In combination in a transmission line including a plurality of sections of outer and inner conductors, means for maintaining concentric spacing between said conductors, means for connecting adjacent sections of outer conductor, and

means for connecting each pair of adjacent sections of inner conductor subject to variations in length, comprising means attachable to one end of each pair of said sections oi inner conductor being connected, a perpiheral depression provided in a portion of each of said attache-ble means, and further means slidable in said depressed portions of said attachable means for enabling said last-mentioned connecting means to be of variable over-all length to compensate for the variations in the lengths of said sections of inner conductor being connected.

2. A concentric conductor line for transmitting high frequency waves including a plurality of sections of outer and inner conductors, means for spacing each inner conductor from its associated outer conductor such that a certain ratio is provided between the inside diameter of said outer conductor and the outside diameter ci said inner conductor, means for connecting adjacent sections of outer conductor such that the inside diameters of said outer conductor sections and said connecting means therefor are substantially uniform, and means for connecting adjacent sections of said inner conductor, said last means having an outside diameter substantially equivalent to the outside diameters of said sections ci inner conductor being connected, and including two spaced peripheral portions whose outside diameters are less than the outside diameters of said inner conductor sections whereby reection effects are effectively introduced at each of said two portions during the transmission of said Waves, and a further portion interposed between said two-portions and having an outside diameter substantially equivalent to the outside diameters of said sections of inner conductor being connected, said further portion having an electrical length of one-quarter wavelength or odd multiple thereof at the mean frequency of said waves to minimize substantially said reflection effects.

3. A transmission line for high frequency waves, including a plurality of sections of outer and inner conductors, means for concentrically spacing said inner conductors from said outer conductors, means for connecting adjacent sections of said outer conductor, and means for connecting each pair of adjacent sections of said inner conductor, which latter sections are subject to variations in length with reference to their associated sections of outer conductor, comprising a plurality of elements of which two elements are attachable to contiguous ends of each pair of adjacent sections of inner conductor, each of said two elements having a peripheral recess in a portion thereof, and a third element slidably engages said recessed portions of said two elements for varying the over-all length of said plurality of elements to compensate for the variations in the lengths of the inner conductor sections being connected.

4. A transmission line for high frequency waves, including a plurality of sections of outer and inner conductors, means for maintaining a spaced relation between said inner and outer conductors, means for connecting adjacent sections of said outer conductor, and means for connecting each pair of adjacent sections of said inner conductor varying in length with reference to the length of their associated outer conductors, comprising a plurality of means, each attachable to the end of one of the two adjacent sections of inner conductor and including a portion formed With a substantially smooth portion, and means interposed between both said attachable means and formed with two spaced smooth portions each of which is capable of engaging said smooth portion` of one of said attachable means at different points for varying the over-al1 length of said last connecting means to compensate for the Variations in the lengths of the inner conductor sections being connected.

5. A transmission line for high frequency waves, including a plurality of sections of tubular outer and inner conductors, means for maintaining concentric spacing between said conductors, means for connecting adjacent sections of outer conductor, and means for connecting each pair of adjacent sections of inner conductor whose lengths, with reference to the associated sections of outer conductor, are subject to variations, comprising a pair of members, each having one end adapted for insertion to a fixed amount in the interior of one inner conductor section and the opposite end formed with a contact surface, and a clamp provided with two spaced contact surfaces each of which engages said contact surface of one of said members, said clamp being slidable axially of said contact surfaces of both said members for varying the over-all length of said connecting means for said inner conductor sections to compensate for variations of the lengths of said last sections.

6. A transmission line according to claim 5 in which said connecting means for each pair of adjacent sections of inner conductor embodies at least one point of an effective outside diameter which is less than the outside diameter of the adjacent sections of inner conductor being con nected whereby reection effects are effectively introduced in the transmission of the waves at said one point, and said clamp has an electrical length equivalent to an odd number of quarter wavelengths at the mean frequency of the waves being transmitted on said line to minimize substantially the introduction of said reflection effects.

7. In combination with a concentric conductor transmission line, including a plurality of sections of tubular outer and inner conductors, means for concentrically spacing said outer and inner conductors, and means for connecting adjacent sections of outer conductor, means for connecting each pair of adjacent sections of inner conductor, which sections tend to vary in length with reference to their associated sections of outer conductor, comprising a pair of plugs each having one end adapted for insertion interiorly of one inner conductor section and its other end formed with a peripheral projection engaging the end of the associated inner conductor section for limiting the amount of such insertion, a flange spaced from said projection, and a shank joining said projection and flange, and a cylindrical clamp including a circular recess at each of its two opposite ends and an annular shoulder at the outermost axial end of each such recess, said nange of each plug being positioned in one recess of said clamp whereby one shoulder of said clamp is held in eng-agement with one shank of each plug, said clamp being adjustable axially of said Shanks of both said plugs within the limits of said projections and flanges thereof for varying the over-all length of said connecting means for said inner conductor sections to compensate for variations of the lengths of said last sections.

ALBERT L. ROBINSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,044,580 Leach June 16, 1936 2,165,961 Cork et al July 11, 1939 2,178,299 Dallenbach Oct. 31, 1939 2,209,152 Daniels July 23, 1940 

